1. Field of the Invention
The present invention relates to a method for making a semiconductor device, and more particularly, to a method for forming a metal pattern for a wiring of a semiconductor device.
2. Description of the Related Art
FIGS. 1A through 1E illustrate, in cross-section, a portion of a semiconductor device as it undergoes conventional processing acts in sequence for forming a metal pattern for a wiring of a semiconductor device.
Referring first to FIG. 1A, a first refractory metal film 2, a metal wiring film 3, and a second refractory metal film 4 are, in this order, deposited on a semiconductor substrate 1. A photoresist film 5 is then deposited on the second refractory metal film 4.
Next, as shown in FIG. 1B, a photoresist pattern 5' is formed by etching the photoresist film 5 through a photolithography process.
Next, the metal films 2, 3 and 4 are etched using the photoresist pattern 5' as a mask, thereby obtaining metal patterns 2', 3' and 4' as shown in FIG. 1C. At this point, the etching process is performed by a dry-etching method using a gas mixture such as BCl.sub.3 /Cl.sub.2 /N.sub.2. During this process, polymer impurity layer 6 is created on an upper surface of the photoresist pattern 5' as well as on side walls of the metal patterns 2', 3' and 4'; (see FIG. 1C). Furthermore, part of the metal wiring pattern 3' is corroded by reacting with the Cl.sub.2 of the gas mixture of BCl.sub.3 /Cl.sub.2 /N.sub.2.
Next, to remove the photoresist pattern 5' and part of the polymer impurity layer 6, the substrate 1 is heat-treated within an ashing chamber at a temperature of about 150-250.degree. C. However, since the polymer impurity layer 6 encloses most of the photoresist pattern 5', the photoresist pattern 5' is not completely removed as shown in FIG. 1D. At this point, the remaining photoresist pattern 5' becomes hardened by the relatively high temperature of about 150-250.degree. C. used in the ashing process.
Following the above, the polymer impurity layer 6 is removed by a chemical wet-cleaning process. However, at this point, since it is impossible to remove the remaining photoresist pattern 5' as a result of the hardening of the same during the ashing process, as shown in FIG. 1E, the remaining photoresist pattern 5' is left on the metal pattern 4' even after the chemical wet-cleaning process. This remaining photoresist pattern 5' makes it difficult to carry out a subsequent metal layer formation process.